Explosive volcanism is the response of magma to rapid decompression. Inherent complexity of volcanoes and lack of observations at depth in young systems are impediments to proper understanding of this important phenomenon. The Katmai Scientific Drilling Project is an interdisciplinary surface and drilling investigation of an exceptionally large and relatively simple explosive volcanic event that occurred in Alaska's Aleutian Range in 1912. The surface phase of the project is now largely complete, and results are presented in the papers that follow. ¿American Geophysical Union 1991